Fabrication and Characterization of Nanopillar-Like HA Coating on Porous Ti6Al4V Scaffold by a Combination of Alkali–Acid-Heat and Hydrothermal Treatments

Porous titanium scaffold with suitable porous architecture exhibits enormous potentials for bone defect repairs. However, insufficient osteointegration and osteoinduction still remain to open as one of the major problems to achieve satisfactory therapeutic effect. To solve this problem, many studies have been carried out to improve the bioactivity of porous titanium scaffold by surface modifications. In this study, porous Ti6Al4V scaffolds were fabricated using additive manufacturing technique. Porous architectures were built up based on a diamond pore structure unit. Alkali–acid-heat (AH) treatment was applied to create a TiO₂ layer on the porous Ti6Al4V scaffold (AH-porous Ti6Al4V). Subsequently, a hydrothermal treatment was employed to enable the formation of HA coating with nanopillar-like morphology on the alkali–acid-heat-treated surface (HT/AH-porous Ti6Al4V). The effects of surface modifications on apatite-forming ability, protein adsorption, cell attachment, cell proliferation and osteogenic gene expression were studied using apatite-forming ability test, protein adsorption assay and in vitro cell culture assay. It was found that the HT/AH-porous Ti6Al4V exhibited the highest apatite formation ability and best affinity to fibronectin and vitronectin. In vitro studies indicated that the mesenchymal stem cells (MSCs) cultured on the HT/AH-porous Ti6Al4V presented improved adhesion and differentiation compared with the porous Ti6Al4V and AH-porous Ti6Al4V.